Roman Abramovich, the Russian billionaire and owner of Chelsea FC, today bowed out of Russian politics when he resigned as governor of the frozen far-eastern province of Chukotka.

Abramovich stepped down as the region's governor at "his own request", the Kremlin said today. Russia's new president, Dmitry Medvedev, had signed a decree relieving him of his duties, it added.

Abramovich had been in the job for seven years and his departure follows at least one unsuccessful earlier attempt to quit last year. Vladimir Putin turned down Abramovich's request and asked him to carry on. He agreed.

Today Abramovich's spokesman said that the oligarch was departing from politics because he considered his job in Chukota completed. Since becoming governor he has pumped billions into the sparsely populated Pacific region, near to Alaska.

"When Mr Abramovich came to Chukotka the region was in serious crisis. In the past seven years he's succeeded not only in pulling it out of crisis but significantly boosting the standard of living," his spokesman, John Mann, told the Guardian.

"He's rebuilt infrastructure, housing, schools and hospitals. He's bought in new investors to build the economy of the region. He's put Chukotka on a great footing for future development," said Mann.

Asked why Abramovich was quitting now, Mann said: "It's very much mission accomplished. But I think there's no overriding reason. I think it's just a change of role."

Abramovich, 41, is Russia's third richest man, according to Forbes Russia magazine, with a $24.3bn (£12bn) fortune.

He has been spending more time recently in Moscow than London, aides say, following his divorce last year.

During the Putin era, Russian oligarchs were obliged to obey the state and to show social responsibility, observers suggest. Those who challenged the Kremlin invariably ended up in exile or in prison.

By taking personal responsibility for Chukotka, one of Russia's most backward and underdeveloped regions, Abramovich showed his loyalty to Putin. He also fended off critics who accused him of unpatriotic behaviour when he bought Chelsea in 2003.

Today analysts suggested that Abramovich had been allowed to give up his government job following Putin's departure as president and the inauguration in May of Dmitry Medvedev as Russia's new leader.

"Putin didn't want him [Abramovich] to leave while power was being transferred," said Sergei Mikheyev, vice-president of Moscow's Centre for Political Technologies. "He asked him to stay on. Now the transfer has happened. The situation has changed."

"Chukotka will really miss him. It is impossible for anybody else to invest as much money into the region," said Mikheyev.

Abramovich was previously Russia's richest man. But he has recently slipped down the table following the sale of his oil firm Sibneft to Gazprom in 2005. Most of his assets are now held by Millhouse Capital, his private investment vehicle.

Last month Abramovich moored his personal $300m yacht in St Petersburg while he attended the annual economic forum in Russia's second city. The British singer Amy Winehouse also played a concert at the opening of an art gallery in Moscow to be managed by Abramovich's girlfriend Daria Zhukova.

Today Mann said that Abramovich would continue to financially support the autonomous district of Chukotka. "Millhouse is investing in several projects there as well as two charities," he said.